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1.
Single-electron transfer (SET) plays a critical role in many chemical processes, from organic synthesis to environmental remediation. However, the selective reduction of inert substrates (Ep/2<−2 V vs Fc/Fc+), such as ubiquitous electron-neutral and electron-rich (hetero)aryl chlorides, remains a major challenge. Current approaches largely rely on catalyst photoexcitation to reach the necessary deeply reducing potentials or suffer from limited substrate scopes. Herein, we demonstrate that cumulenes–organic molecules with multiple consecutive double bonds–can function as catalytic redox mediators for the electroreductive radical borylation of (hetero)aryl chlorides at relatively mild cathodic potentials (approximately −1.9 V vs. Ag/AgCl) without the need for photoirradiation. Electrochemical, spectroscopic, and computational studies support that step-wise electron transfer from reduced cumulenes to electron-neutral chloroarenes is followed by thermodynamically favorable mesolytic cleavage of the aryl radical anion to generate the desired aryl radical intermediate. Our findings will guide the development of other sustainable, purely electroreductive radical transformations of inert molecules using organic redox mediators.  相似文献   

2.
《中国化学》2017,35(11):1661-1664
((2S ,4R )‐4‐Hydroxy‐N ‐(2‐methylnaphthalen‐1‐yl)pyrrolidine‐2‐carboxamide (HMNPC), an amide derived from 4‐hydroxy‐L ‐proline and 2‐methyl naphthalen‐1‐amine, is a powerful ligand for Cu‐catalyzed coupling of (hetero)aryl halides with sulfinic acid salts, allowing for first time the metal‐catalyzed coupling of (hetero)aryl chlorides and NaSO2Me. A considerable number of (hetero)aryl chlorides worked well, providing the pharmaceutically important (hetero)aryl methylsulfones in good to excellent yields.  相似文献   

3.
A new and one-pot synthesis of novel alkynyl/alkenyl/aryl (hetero)aryl substituted 3,4-dihydropyrimidin-2(1H)-one derivatives has been developed via a multi-component reaction involving sequential phosphorus acid-mediated solvent-free Biginelli followed by copper-free Sonogashira or Heck or Suzuki reaction.  相似文献   

4.
Low-Temperature 13C-NMR. Spectroscopy of Organolithium Derivatives. - 13C, 6Li-Coupling, a Powerful Structural Information The 13C-NMR. spectra of thirteen lithiated hydrocarbons ( 1c–13c . Table 2) and of eighteen a-halo-lithium carbenoids ( 14c–31c , Table 3) have been recorded in donor solvent (R2O, R3N) mixtures at temperatures down to ?150°. The organolithium species were generated from singly or doubly 13C-labelled precursors by H/6Li- or Br/6-exchange. - 13C, 6Li-Coupling was observed of all species but those which supposedly contain contact ion pair C,Li-bonds (benzylic and acetylenic derivatives). The multiplicities of the signals are correlated with the degree of aggregation in solution: the triplets of the halocarbenoids must arise from monomers or heteroatom-bridged oligomers, the quintuplets of butyl-, cyclopropyl-, bycyclo[1.1.0]butyl-, vinyl-, and phenyllithium from dimers with planar arrangement of two Li- and two C-atoms, as known from crystal structures (Scheme 3). All 13C, 6Li-couplings are temperature-dependent, dynamic processes cause them to disappear above ca. ?70° (Fig. 1–4). - Types of organolithium compounds are categorized according to the change of chemical shift δΔ (H, Li) upon H/Li-substitution, according to the 13C, 6Li-coupling constants ranging from 0 to 17 Hz, and according to the multiplicities which indicate the aggregation: type A are Li-derivatives of alkanes and cycloalkanes, type B are s?-bonded vinyl, aryl, and alinyl derivatives, type C are a-heterosubstituted (RS, hetero=halogen) organolithium compounds, and type D are π-bonded allylic and benzylic systems (Table 5). The C,Li-distances in the crystal structures of representatives of all four classes are within the small range of 2.18–2.28 Å (cf. Scheme 3). - Some surprising observations and their interpretations and consequences are: (a) butyllithium solutions in THF, THF/TMEDA, and dimethyl ether contain increasing amounts of dimer upon cooling, the equilibrium (tetramer · 4 THF)+4 THF ? 2 (dimer · 4 THF) being shifted to the right (Fig. 1 and Scheme 4); thus, more of a different species is present at low temperatures, with the accompanying changes in reactivity; (b) mixed higher aggregates are formed upon addition of butyllithium to bicyclobutyllithium; these are broken up to dimers upon addition of TMEDA (Tetramethylethylene-diamine) (Fig. 2 and Scheme 5); (c) the solid state, the calculated gas-phase and the solution species of phenyllithium all have dimeric structures, and so do vinyl and cyclopropyl lithium derivatives; the 13C-deshielding observed upon replacement of H by Li on sp2- and sp-C-atoms is related to a polarization of the π-electrons (Table 3, Fig. 3 and Scheme 6); (d) the spectra of halo-lithium carbenoids show three striking features as compared to the C,H-compound: deshielding of up to 280 ppm (Table 3), strong decrease of the coupling constant with 1H- and 13C-nuclei attached to the carbenoid C-atom (Table 4), and a structure-independant, almost constant, large 13C, 6Li-coupling constant of 17 Hz (Table 3); as shown in Scheme 7, these effects might be the consequence of a reduced degree of hybridization of the carbenoid C-atom. - The preparation of the labelled compounds and the generation of solutions of the organolithium compounds for NMR. measurements are described in full detail.  相似文献   

5.
The treatment of various N‐morpholino amides with TMPZnCl⋅LiCl (TMP=2,2,6,6‐tetramethylpiperidyl) and Mg(OPiv)2 in THF at 25 °C provides solid zinc enolates with enhanced air and moisture stability (t 1/2 in air: 1–3 h) after solvent evaporation. These enolates undergo Pd‐ and Cu‐catalyzed cross‐couplings with (hetero)aryl bromides as well as allylic and benzylic halides. The arylated N‐morpholino amides were converted into various ketones by LaCl3⋅2 LiCl mediated acylation with Grignard reagents. The new, solid enolates were used to prepare a potent anti‐breast‐cancer drug candidate in six steps and 23 % overall yield.  相似文献   

6.
This paper contains the synthesis and characterization of the seven new benzimidazolium salts and their corresponding new palladium(II)‐NHC complexes with the general formula [PdX2(NHC)2], (NHC = N‐heterocyclic carbene, X = Cl or Br), and also their catalytic activity in direct C‐H bond arylation of 2‐substituted furan derivatives with aryl bromides and aryl chlorides. Under the optimal conditions, these palladium(II)‐NHC complexes showed the good catalytic performance for the direct C‐H bond arylation of 2‐substituted furans with (hetero)aryl bromides, and with readily available and inexpensive aryl chlorides. The C‐H bond arylation regioselectively produced C5‐arylated furans by using 1 mol% of the palladium(II)‐NHC catalysts in moderate to high yields.  相似文献   

7.
《Mendeleev Communications》2022,32(2):258-259
A new efficient solvent-free procedure for the CO cross-coupling between (hetero)aryl halides with phenols, primary alkanols, or (hetero)arylmethanols using Pd2(dba)3/ButBrettPhos catalytic system is proposed using 23 examples.  相似文献   

8.
New Schiff base derivatives, 2,2′‐[naphthalene‐2,7‐diylbis(oxy)]bis[N′‐substituted acetohydrazide] ( 4a‐m ) were synthesized by the acid catalyzed condensation of aryl/hetero aromatic aldehydes with 2,2′‐ [naphthalene‐2,7‐diylbis(oxy)]diacetohydrazide ( 3 ) under reflux temperature and ultrasonic irradiation. These Schiff base derivatives were confirmed through spectral characterization using IR, 1H NMR, 13C NMR and mass spectra. All the synthesized compounds were screened for their antioxidant activity using DPPH free radical scavenging method.  相似文献   

9.
An efficient method for the preparation of 2‐substituted 4‐aryl‐4,5‐dihydro‐3,1‐benzoxazepine derivatives under mild conditions has been developed. The reaction of 2‐(2‐aminophenyl)ethanols 1 with acid chlorides in the presence of excess Et3N in THF at room temperature gave the corresponding N‐acylated intermediates 2 , which were dehydrated by treatment with POCl3 to give 2‐substituted 4‐aryl‐4,5‐dihydro‐3,1‐benzoxazepines 3 in a one‐pot reaction.  相似文献   

10.
meso‐Tetraarylporphyrinato complexes 1a – g (ZnII, CuII, and NiII) bearing one or two nitro‐substituted aryl moieties react with 1,1,1‐trimethylhydrazinium iodide in the presence of tBuOK in THF at 0–5° or in the presence of KOH in DMSO at 60–70° according to a nucleophilic substitution of an H‐atom, thus affording porphyrins 2a – g and 3f , g with amino‐functionalized meso‐positioned aryl substituents in yields up to 73% (Scheme 1 and Table). The products obtained are attractive intermediates for further derivatization of porphyrins and may be of potential use as sensitizers in photodynamic cancer therapy.  相似文献   

11.
12π-Tetraazapentalenes, 2,3-disubstituted 6,7-dihydro-5H-2a-thia(2a-SIV)-2,3,4a,7a-tetraazacyclopent-[cd]indene-1,4(2H,3H)-dithiones, 1 and 7 , reacted with excess alkyl or aryl isothiocyanates and isocyanates to afford mono- and di-alkyl or aryl substituted tetraazapentalene derivatives which have the thiocarbonyl and carbonyl groups.  相似文献   

12.
13.
A ruthenium‐catalyzed carbonylative C?H bond arylation process for the three‐component synthesis of complex aryl–(hetero)aryl ketones in an aqueous solution has been developed. By exploiting the ortho‐activating effect of nitrogen‐containing directing groups, a regioselective, successive twofold C(sp2)?C(sp2) bond formation has been achieved. This straightforward catalytic process provides access to versatile products prevalent in multiple bioactive compounds and supplies a valuable functional group for subsequent transformations.  相似文献   

14.
This Review discusses the various methods for functionalizing pyridine and quinoline scaffolds, including direct selective metalation (DoM), halogen/metal exchange reactions, Li, Mg, and Zn insertion, and trans-metalation approaches, which are then followed by cross-coupling reactions of the Kumada or Negishi types. Selective deprotonation of aryl or pyridyl/quinolinyl derivatives can be performed using n-BuLi, LDA, and TMP-based different organolithium, -magnesium, and -zinc reagents. The functionalized pyridine and quinoline-based heterocyclic compounds were prepared by selectively deprotonating with presenting a directing functional group substituted pyridine/quinoline analogues in the presence of TMP-bases (TMP−Li, Mg, Zn reagents). Different aryl or alkyl Li, Mg, and Zn reagents with electron-donating and electron-withdrawing substituents undergo transition metal-catalyzed C(sp2)−C(sp2) and C(sp2)−C(sp3) types of cross-coupling reactions with pyridine/quinoline halides under mild conditions with the sustainable process producing complex N-heterocycles. Using moderate and sustainable reaction conditions, sensitive functional group tolerance, and inexpensive and low toxic chemicals, highly functionalization of pyridine and quinoline-based bioactive therapeutic scaffolds and natural products was accomplished. Therefore, in this article, we provide a succinct overview of the numerous synthetic strategies and practical methods used by various authors between 2010 and 2023 to functionalize pyridine and quinoline analogues using diverse Li, Mg, and Zn organometallic reagents.  相似文献   

15.
Two efficient methods for the preparation of 2‐(2‐sulfanyl‐4H‐3,1‐benzothiazin‐4‐yl)acetic acid derivatives 3 under mild conditions have been developed. The first method is based on the reaction of 3‐(2‐isothiocyanatophenyl)prop‐2‐enoates 1a – 1c with thiols in the presence of Et3N in THF at room temperature, leading to the corresponding dithiocarbamate intermediates 2 , which underwent spontaneous cyclization at the same temperature by an attack of the S‐atom at the prop‐2‐enoyl moiety in a 1,4‐addition manner (Michael addition) to give 2‐(2‐sulfanyl‐4H‐3,1‐benzothiazin‐4‐yl)acetates in one pot. The second method involves treatment of 3‐(2‐isothiocyanatophenyl)prop‐2‐enoic acid derivatives 1b – 1d with Na2S leading to the formation of 2‐(2‐sodiosulfanyl‐4H‐3,1‐benzothiazin‐4‐yl)acetic acid intermediates 5 by a similar addition/cyclization sequence, which are then allowed to react with alkyl or aryl halides to afford derivatives 3 . 2‐(2‐Thioxo‐4H‐3,1‐benzothiazin‐4‐yl)acetic acid derivatives 6 can be obtained by omitting the addition of halides.  相似文献   

16.
A series of 6‐amino‐8‐aryl‐3,4‐dihydro‐1H‐spiro[naphthalene‐2,2'‐[1,3] dioxolane]‐5,7‐dicarbonitrile and 8‐arylidene‐4‐aryl‐7,8‐dihydro‐5H‐spiro[quinazoline‐6,2'‐[1,3] dioxolan]‐2‐amine derivatives have been synthesized from the reactions of 1,4‐dioxaspiro[4.5] decan‐8‐one, aromatic aldehydes, and malononitrile (or guanidine carbonate) under different conditions with high yields. In this research, it was found the DBU–THF was efficient reaction condition for obtaining 6‐amino‐8‐aryl‐3,4‐dihydro‐1H‐spiro[naphthalene‐2,2'‐[1,3]dioxolane]‐5,7‐dicarbonitrile derivatives, while 95% EtOH and NaOH was the preferred condition for the synthesis of 8‐rylidene‐4‐aryl‐7,8‐dihydro‐5H‐spiro[quinazoline‐6,2'‐[1,3]dioxolan]‐2‐amine derivatives. To the best of our knowledge, these Spiroheterocycles were first reported in our research. The other advantages of this process were short‐reaction time, wide scope substrates, and simple set‐up.  相似文献   

17.
A palladium(II)-catalyzed decarboxylative protocol for the synthesis of aryl ketones has been developed. The addition of TFA was shown to improve the reaction yield and employing THF as solvent enabled the use of solid nitriles and in only a small excess. Using this method, five different benzoic acids reacted with a wide range of nitriles to produce 29 diverse (hetero)aryl ketone derivatives in up to 94% yield.  相似文献   

18.
A single set of reaction conditions for the palladium‐catalyzed amination of a wide variety of (hetero)aryl halides using primary alkyl amines has been developed. By combining the exceptionally high reactivity of the Pd‐PEPPSI‐IPentCl catalyst (PEPPSI=pyridine enhanced precatalyst preparation, stabilization, and initiation) with the soluble and nonaggressive sodium salt of BHT (BHT=2,6‐di‐tert‐butyl‐hydroxytoluene), both six‐ and five‐membered (hetero)aryl halides undergo efficient and selective amination.  相似文献   

19.
Decarboxylative cross‐coupling reactions of substituted 2‐carboxyazine N‐oxides, with a variety of (hetero)aryl halides, by bimetallic Pd0/CuI and Pd0/AgI catalysis are reported. Two possible pathways, a conventional bimetallic‐catalyzed decarboxylative arylation, as well as a protodecarboxylative/direct C?H arylation sequence have been considered. These methods provide the first general decarboxylative arylation methodology for the 2‐carboxyazine series.  相似文献   

20.
An efficient domino cyclization method for the construction of aza‐podophyllotoxin/aza‐conidendrin derivatives has been established. Reactions of different dienes with aryl halides in the presence of a palladium catalytic system produced different kinds of podophyllotoxin derivatives through a highly regioselective C? H functionalization. Treatment of dienes with aryl halides that have electron‐withdrawing substituents on the phenyl ring created aza‐podophyllotoxin derivatives by means of the functionalization of the C? H bonds ortho to the C? halide bonds of the incoming aryl halides. The reaction of dienes with 1‐iodobenzene or aryl halides that incorporate electron‐donating groups produced aza‐conidendrin derivatives by means of the functionalization of both sp3 C? H and sp2 C? H bonds. The regioselective C? H functionalization for the formation of different pseudo‐podophyllotoxin/‐conidendrin derivatives is proven by analyses of the 1H NMR spectra of the products and selective X‐ray analyses of the structures of the products. Thus, the palladium‐catalyzed domino cyclization of 1,6‐dienes for the preparation of aza‐podophyllotoxin/aza‐conidendrin derivatives can be controlled by selectively controlling the C? H functionalization.  相似文献   

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